<p>This retrospective clinical study aimed to investigate the long-term clinical performance of glass-based ceramic onlay restorations in terms of survival rate, types of failure, and patient satisfaction over an eleven-year follow-up period. Glass-based ceramics are increasingly preferred in restorative dentistry for their mechanical resilience and superior optical properties, which meet the requirements of modern minimally invasive and esthetic approaches. A total of 115 indirect glass-based ceramic onlay restorations, placed between 2012 and 2023, were retrospectively analyzed. Clinical records were reviewed to determine restoration survival and failure types. Patient satisfaction was assessed using a numerical rating scale ranging from 0 to 10. Statistical analyses were performed to evaluate potential influencing factors such as marginal integrity, tooth location, and restorative procedures. The overall survival rate was 87.9%. The most common causes of failure were ceramic fracture (6.0%) and adhesive debonding (5.2%). Patient satisfaction was generally high, with mean scores above 8. Tooth position and marginal adaptation were statistically significant factors affecting restoration longevity. Glass-based ceramic onlay restorations demonstrated high long-term clinical success and patient satisfaction, supporting their use as conservative and esthetic alternatives to full-coverage crowns. These findings suggest that such restorations can be reliable long-term treatment options, provided proper material selection, tooth preparation, and bonding protocols are followed.</p>